This application claims the priority of German application 197 17 042.0, filed Apr. 23, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process for shifting a gear change transmission having no synchronizing members, and more particularly, to a process for shifting a gear change transmission having no synchronizing member from an old gear into a new gear without the interruption of the drive connection between the gear change transmission and an internal-combustion engine used as the driving engine and using form-locking gear clutches for coupling a respective gearwheel to its transmission shaft. In a process step triggered by a shifting signal, first the engine torque is reduced and then the gear clutch of the old gear is disengaged, and, in a further process step, when the old gear is disengaged, the rotational engine speed is changed in the direction of the synchronous rotational speed pertaining to the new gear, and, in a further process step, the rotational engine speed--if it is within the range of the synchronous rotational speed--is maintained at a significant value for a defined time period and, in this time period, the gear clutch of the new gear is engaged.
DE 35 07 565 C2 describes a device which operates for establishing the synchronous running of a position change transmission having no shifting clutch members and no synchronizing members for a vehicle, such as a motor vehicle, equipped with an internal-combustion engine as the driving engine. The device is equipped with at least one system for influencing the torque output of the internal-combustion engine, a transmission control unit and means for determining the synchronous point of the position change transmission. During gear shifting, the rotational speed of the internal-combustion engine is changed after the disengagement of the old gear to the rotational speed corresponding to the new gear and, when the synchronous point is reached, the new transmission gear is engaged.
In order to avoid the engagement of the preselected gear from taking place before the synchronous point of the transmission members to be coupled has already clearly been exceeded because the entire arrangement and particularly the mechanical devices for the gear shifting generally are subject to inertia, and in order to thus permit a comfortable, no-jolt engaging of a new transmission gear without the aid of special mechanical synchronizing members, the known device uses a method of operation such that, when the synchronous point is achieved, the torque influencing device can abruptly be acted upon for adjusting such a low torque of the internal-combustion engine that the rotational speed of the internal-combustion engine remains constant or changes only slightly.
An object of the present invention is to keep the shifting forces for engaging the form-locking gear clutches required as low as possible. According to the present invention, this object has been advantageously achieved by providing a process wherein in the process step triggered by the shifting signal, the engine torque is first raised in the coasting operation, and in that the significant value of the engine rotational speed is assigned to a defined rotational speed difference at the gear clutches such that the respective drive-side clutch half, during all shifts, either always has the higher or always has the lower rotational speed with respect to the rotational speed of the output-side clutch half.
During each gear change in the process of the present invention, only one and the same of the two engaging flanks of a clutch tooth of a clutch half of the participating gear clutch can come in contact with an engaging flank of the other clutch half which is adjacent in the circumferential direction. Thereby, a symmetrical chamfering angle or chamfering angles on the two engaging flanks of a clutch tooth is or are no longer required. Such a chamfering angle always results in an axial force component which limits the shifting comfort.
Therefore, in the process according to the present invention, the use of gear clutches, in which one engaging flank of a clutch tooth is situated completely in a plane containing the clutch axis, has been found advantageous.
In the process according to the invention, the synchronous rotational speed can be adjusted such that a residual differential rotational speed remains, specifically such that the rotational speed of the engine-side transmission elements (gear wheel) is higher than the rotational speed of the output-side transmission elements (clutch sleeve). Advantageously, these differential rotational speeds are between 10 min.sup.-1 and 40 min.sup.-1.
In the process of the invention, the shifting of the respective gear wheel clutch always takes place such that the same engaging flanks of the clutch teeth strike against one another, irrespective of whether it is an upshift or a downshift.
Thus the engaging flanks of the respective clutch tooth can be configured such that one engaging flank has no chamfering angle, and the other engaging flank is provided with a chamfering angle. Thereby, the clutch teeth of the two clutch halves always strike against one another with the straight engaging flanks and, as a result, only circumferential forces are generated which reduce the remaining differential rotational speed. No axial forces are generated which would counteract the shifting force. The chamfering angle of the second engaging flank permits an axial engaging of the clutch teeth when sweeping over the differential angle between two opposite clutch teeth.
The present invention also relates to a testing step for initiating or terminating a process step under defined conditions.